1. Field of the Invention
The present invention relates to a data driver, a light emitting display device using the same, and a method of driving the light emitting display device, and more particularly to, a data driver adapted to display images with substantially uniform brightness, a light emitting display device using the same, and a method of driving the light emitting display device.
2. Discussion of Related Art
Recently, various flat panel display devices (FPD) with lower weight and volume than cathode ray tubes (CRT) have been developed. The FPDs include liquid crystal display devices (LCD), field emission display devices (FED), plasma display panels (PDP), and light emitting display devices.
Among the FPDs, the light emitting display devices display images using electroluminescent (EL) devices that generate light by re-combination of electrons and holes. The light emitting display device has high response speed and is driven with low power consumption.
The light emitting display device includes pixels positioned in the crossing areas between directions of data lines and scan lines. The pixels are selected when scan signals are supplied to the scan lines to charge the pixels with voltages corresponding to the data signals supplied to the data lines. The pixels supply currents corresponding to the charged voltages to the EL device to generate light of predetermined brightness. The light of the predetermined brightness that is emitted from each of the pixels forms a component of light and the components are combined to display a predetermined image in a display region.
Therefore, the light emitting display device includes a data driving part for supplying data signals to the data lines and a scan driver for supplying scan signals to the scan lines. The data driving part includes at least one data driver having predetermined channels.
FIG. 1 illustrates a conventional data driver 60. For the sake of convenience, in FIG. 1, it is assumed that the conventional data driver 60 includes j (j is a natural number) channels.
Referring to FIG. 1, the conventional data driver includes a shift register unit 1, a sampling latch unit 2, a holding latch unit 3, a signal generator 4, and an output stage 5.
The shift register unit 1 receives a source start pulse SSP and a source shift clock SSC from the outside. The shift register unit 1 sequentially generates j sampling signals while shifting the source start pulse SSP every one period of the source shift clock SSC. Therefore, the shift register unit 1 includes j shift registers 11 to 1j. 
The sampling latch unit 2 sequentially stores data Data in response to sampling signals sequentially supplied from the shift register unit 1. Therefore, the sampling latch unit 2 includes j sampling latches 21 to 2j for storing j data Data.
The holding latch unit 3 receives the data Data from the sampling latch unit 2 to store the data Data. The holding latch unit 3 supplies the data Data stored therein to the signal generator 4. Therefore, the holding latch unit 3 includes j holding latches 31 to 3j. 
The signal generator 4 receives the data Data supplied from the holding latch unit 3 to generate j data signals to correspond to the received data Data. Therefore, the signal generator 4 includes j digital-analog converters (DAC) 41 to 4j. That is, the signal generator 4 generates j data signals using the DACs 41 to 4j provided in the channels to supply the generated data signals to the output stage 5.
The output stage 5 supplies the j data signals supplied from the signal generator 4 to j data lines D1 to Dj. Then, the data signals are supplied to the pixels so that a predetermined image is displayed.
However, according to the conventional data driver, it is generally not possible to generate uniform data signals due to deviation in the DACs 41 to 4j provided in the channels. Actually, even if manufacturing processes are precisely controlled when the DACs 41 to 4j are manufactured, the DACs 41 to 4j typically have deviation of about ±3 mV. Therefore, although the data Data having the same gray scale values are input to the DACs 41 to 4j, data signals having different voltage values (or current values) are generated. As described above, when the data signals having different voltage values (or current values) are generated when the same gray scale values are input to the DACs 41 to 4j, an image with non-uniform brightness is displayed on the light emitting display device. In particular, when the DACs 41 to 4j having high deviation are adjacent to each other, noise in the form of vertical lines is additionally generated.
Therefore, there is a need for reducing the non-uniformity in image brightness that is caused by non-uniformity in fabrication and processing of the digital to analog converters used in data drivers of light emitting display devices.